Starting circuit for electric discharge devices



Nov. 25, 1941.

C. P. STOCKER STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed April 3; 19:59

' 4 Sheets-Sheet 1 ZNVENTOR.

BY I QZ M Q J:

Nov. 25, 1941. c, STOCKER 2,264,055

STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed April 3, 1939 I 4 SheetsSheet,2

HAAME/VT L055 F. 184770 of START/W6 TEA VJ'FOKMEF ill.

Obamanfifilaa/Eer INYfENToR Nov. 25, 1941. c. P. STOCKER 2,264,055

STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed April 3, 1939 4 Sheets-Sheet 3 INVENTOR.

ATTORNEY.

Nov. 25, 1941. c. P. STOCKER 2,264,055

STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed April 3, 1939 4 Sheets-Sheet 4 INVENTO-R.

Qmm wm.

ATTORNEY.

Patented Nov. 25, 1941 STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Closman P. Stocker, Lorain,.0hio, assignor, by

direct and mesne assignments, to Gene ral Electric Company, a corporation of New York Application April 3, 1939, Serial No. 265,645

3 Claims. (01. 176-124) My invention relates to electric discharge devices generally and more particularly to methods and apparatus for starting and operating such devices from a suitable source of electric current. In particular my invention starts and operates electric discharge devices from either alternating current or direct current without moving parts. as related to methods and'apparatus for use on alternating current circuits because of the lower losses and greater use of this form of electric energy.

One of the objects of my invention is to provide an exceedingly simple circuit'for automatically starting and operating electric discharge devices without the use of moving parts.

An object of my invention is to produce auxiliary discharges at the main electrodes of the "discharge lamp to increase the ease with which the lamp ignites.

Another object of my invention is to heat thefilaments of a discharge lamp sufliciently to maintain an auxiliary discharge at each filament before igniting the discharge lamp and to maintain sufiicient voltage between the two auxiliary discharge paths to ignite the gaseous discharge lamp.

Another'object of my invention is to start electric discharge lamps equipped with filaments in the following sequencer a. Beat filaments.

2). Cause auxiliary discharge.

Preference is given to my invention c. Maintain potential difference between main charge lamp.

Another object of my invention is to use a leakage type transformer in combination with an electric discharge lamp equipped with filaments to produce the above mentioned sequence of operation.

Another object of my invention is to cause suba starting mechanism which increases the life of the discharge tube.

Another object of my invention is to maintain a reduced current flow through the filaments of a low voltage electric discharge lamp during normal operation of the lamp.

Another object of my invention is to utilize the combination of filament heating and an auxiliary arc discharge during the starting conditon of the lamp and to extinguish the auxiliary arc, and to maintain a reduced acurrent flow through the filament during the time the lamp is in normal operation.

Another object of my invention is to prevent cooling of filaments in an electrical discharge lamp when operating the lamp in flasher service.

Another object of my invention is to provide a method of flashing electric discharge devices and maintain substantially normal lamp life in flasher service.

My invention is particularly adapted to starting and operating low voltage gaseous electric discharge lamps containing a,rare or monatomic gas such as argon or neon, or certain metallic vapors, such as sodium, mercury, or any other tion of the lamp because of the increased current flow through the current limiting impedance. In the working of my invention the untuned current shunting means may comprise a transformer, a saturable inductance .or a nonlinear resistance. In general I refer to these untuned circuit shunting means as a non-linear impedance element or specifically to the type of unit used. The current limiting impedance will stantially instantaneous starting of electric dis- 5 charge lamps having filaments.

Another object of my invention is to provide a starting and operating arrangement in which the losses during operation are exceptionally low.

be referred to as a linear inductance or a linear resistance or a linear impedance.

A typical starting arrangement of the prior art may comprise a relay arranged to connect the filaments in series and then disconnect theserles filament circuit to allow the discharge to take place. This and other arrangements are described in the article entitled Low voltage Another object of my invention is to provide fluorescent lamp by G. E. Inman and R. N.

Thayer in Electrical Engineering, June, 1938, P ge 245.

Other methods have been proposed in which a vibrating reed is used to strike a piezo-electric crystal, and thereby generates sumcient voltage to start the discharge device similar to the starting arrangement described in, U. S. Patent 2,123,056 to Eugene Lemmers.

My invention improves upon the prior art by automatically starting electric discharge lamps without moving parts and without the use of exceptionally high starting voltages. At the same time, low losses are maintained in the starting unit.

While I have described my invention with reference to electric discharge lamps containing one or more filaments similar to the typical commercial 15 and 20-watt fluorescent low voltage lamps, operated on 110 volts alternating current, it is to be understood that ,my invention is not to be limited to these or any other specific type of gaseous or vapor lamp.

Other objects and features of my invention, thenovel features of which are particularly pointed out in the claims appended hereto, may be more readily and more fully understood from the following description when read with reference to the accompanying drawings, in which like parts of my invention are designated by like reference characters and in which:

Figure 1 shows an enlarged view of one of the main electrodes in the low voltage gaseous dis- :harge lamp, and shows in detail, the electrodes for furnishing the auxiliary discharge. as related 50 the filament.

Figure 2 shows an enlarged view of a main electrode in which the auxiliary discharge is adapted to 'take place between the lead in wires to the filament.

Figure 3 shows my invention using a transformer and an inductance as applied to a lowvoltage gaseous discharge lamp for operation on alternating current. v

Figure 4 shows a modification of my invention as shown in Figure 3 as one possible method of arriving at an optimum operating condition for my invention when used in conjunction with a v discharge lamp.

Figure 5 shows how the total losses and the losses of the individual units may vary with the ratio of the exciting winding to the total winding on the starting transformer. The total losses include the energy required to maintain the filaments at a reduced heat as well as the losses in the individual units when the discharge lamp is in operation.

Figure 6 shows my invention as applied to an auto-type leakage reactance transformer.

. Figure 7 is a modification of my invention as shown in Figure 1 in which the electric discharge lamp is started with one electrode cold.

Figure 8 shows another embodiment of my invention in which a substantially linear inductance is used as a current limiting impedance and in which a saturable inductance is connected in series with the filaments of the electric discharge lamp and in parallel with the lamp.

In Figure 9 -I show a generalized startingcircuit in which the series impedance may be any suitable linear impedance and where the untuned current shunting means may be any suitable nonlinear impedance. By using a linear resistance for the current limiting impedance and a suitable non-linear resistance connected in series with the filaments and in parallel with the discharge lamp,

,my invention becomes a universal starting device capable of operating upon either alternating current or direct current without moving parts.

Figure 10 shows my invention using the saturable transformer modified to start the electric discharge lamp with one electrode cold.

In Figure 11 my invention is shown adapted to be used for flashing an electric discharge lamp. In this circuit the filament heating and auxiliary arc discharges are used to obtain prompt ignition and during the time the lamp is lighted the filaments are maintained at a reduced heat and auxiliary arcs extinguished.

Electric discharge lamp starters of the prior art have in general, one disadvantage and that is starting or ignition of the lamp is erratic. By this I mean that these starters fail, in many cases, to cause ignition of the lamp on the first impulse. Such lamp starters may make as many as three or four attempts before ignition occurs.

- In a typical starter which is commercially available, the ignition of the lamp is controlled by a thermal element. With this type of starter an elapsed time of several minutes may be necessary for the thermal element to cool between starts. Another disadvantage of starters of the prior art is that should the electric discharge lamp deteriorate after a long and useful life, so that the main arc discharge conducts less than normal rated current, the starter may fail to remain in an operated position, in which case the starter operates and releases.- In some tests which I conducted and in which the lamp current decreased to a value below normal, I found that the starters were destroyed because of welding of the starting contacts. This occurs when the lamp starter attempts to start a lamp which will not remain ignited but which does not have burned-out filaments. Another disadvantage of the present commercially available starters is that they are delicate and the adjustment easily destroyed ifdropped or mistreated. Since the commercially available starters are delicate and the adjustment easily destroyed they may require frequent maintenance and accurate adjustments which are costly and bothersome.

With my invention, I overcome these difilculties. A lamp starter made in accordance with my invention is rugged and able to withstand shocks and jars without harmful efiects. In normal operation, my lamp starter causes substantially instantaneous ignition in the lamp and does not depend upon thermal elements or moving parts to perform this operation. Because of these characteristics, alamp starter made in accordance with my invention may be used for flasher service because of its prompt and positive action in causing electric discharge lamps to ignite. Also, my invention can be made physically small so as to be easily mounted in-a molding such as may be associated with the electric discharge lamp and lastly, the starting mechanism is foolproof and self-protecting in case of lamp deterioration or failure.

In typical low voltage discharge lamp starting units, commercially available today, a high transient starting voltage is applied across the main electrodes of the lamp as a starting condition. With this type of starter the inductance is connected in series with the discharge lamp and a source of alternating-current. By interrupting the flow of current through the inductance without disconnecting the inductance from the lamp The current interrupting device may comprise contacts which connect the two filaments of the low voltage electric discharge lamp in series,

without any impedance between thefilaments.

The interruption causes the series inductance to impress a high transient voltage upon the lamp as previously explained. It should be notedthat in this type of startera potential sufiicient to ignite the lamp is not impressed upon the lamp until the circuit heating the filaments is broken. Tests show, that depending upon the temperature of the lamp and filament at the time the circuit is interrupted, that voltages as high as 300 volts R. M. S. values are impressed upon the tube to cause ignition with this type of starter. Experiments indicate that the high voltage applied to the lamp for starting, tends to rapidly deteriorate the coated filaments of the lamp. It is believed that the coating on the filaments of the lamp rapidly disappears from the filament because the filament is bombarded and the coating knocked off by high speed gas molecules.

To overcome this I employ in conjunction with i the heated filament, an auxiliary discharge for producing ionization in the lamp. Referring to Figure 1, I show an enlarged'view of a main electrode comprising auxiliary electrodes 2| and 22 shunted by a filament II as used in my invention. I have found that the starting voltage can Normal operating voltage across this particular tube was 65 volts. '1 Thus it can be seen that as soon as the auxiliary arc has reached a stable value, the ignition voltage of the'lamp'is approximately the operating voltage.

In experiments, .it is curious to note that with a series impedance, the filament shunted by the auxiliary arc maintains a substantially constant voltageacross the filament terminals within wide variations of current. While I have not shown in the'table, values beyond .8 ampere, I have gradually increased the current into the filament and auxiliary discharge to 8 amperes which is ten times the maximum current value shown in the chart. With 8 amperes through the filament and auxiliary arc, the voltage across theterminals was still substantially constant. It is believed that under this condition, the filament receives practically a constant amount of current and all excess current'is passed through the auxiliary arc stream. Thus the auxiliary discharge path protects the filaments by maintaining a substantially constant voltage across the filament. At the same time ionization of the gas by the auxiliary discharges conditions the lamp for ready ignition at low voltage. However, once a saturating value of ionization is reached, no noticeable improvement in starting results from' increased current flow-through the auxiliary arc stream. By saturating value"; referred to in'the table, I mean that'the voltage drop across the filament, and the auxiliary electrodesbecomes substantially: constantafter .the'auxlliaryarc-ls be materially reduced if an auxiliary arc is maintained between the auxiliary electrodes 2| and 22 during the time a potential is impressed across gestablished. "It;is t'obe clearly understood that ,the saturating value referred to in connection ,with this table does not pertain to the saturation the lamp. It will be noted from the table below I that a potential only slightly higher than the potential used for normal lamp operation will cause ignition when an auxiliary arc discharge is used. Below is a table taken from actual data on a typical 20-watt low voltage fluorescent elec-. tric discharge lamp showing ignition voltage as applied across the lamp as compared with filament and auxiliary discharge current at the starting electrodes. I

R. M. S. voltage applied across lamp sufficient Filament and auxiliary discharge current to cause ignition 0 Y 320-325 g ycles i. N3 clfillellt tgrough auxiliary are ggg i gi g f 3 98 237 Gil-cycles A. 230 (iii-cycles A. 188 fill-cycles A.

148 60-cycles A.

' 130 (SO-cycles A.

125 (SO-cycles A.

70-80 Gil-cycles A. C.

70-80 (SO-cycles A. C.

.41 (auxiliary discharge across one'filamen .5 (auxiliary discharge across both filaments).

. 55 (auxiliary discharge across both filaments).

.6 (auxiliary discharge across both filaments).

.7 (auxiliary discharge across both filaments) saturating value.

.8 (auxiliary discharge across both filaments) saturating value.

' discharge occursthrough gapi42.

together with lead-in wires l9 and 20 constitute of any of the-inductance elements or transformer referred to later in this specification.

With this in mind, it can be easily seenthat it is possible, to start the low voltage electric dischargedamp upon ignitionvoltages which may be approximately as low as normal operating voltage of the lamp. I

Referring to Figure l, filament I4 is adapted tobe heated from an external source, by means of lead-in wires I9 and 20. Auxiliary electrodes 2| and 22 are connected directly to lead-in wires I9 and 20 respectively. The auxiliary arc is passed through gap 23 between electrodes 2| and 22.

charge tube herein considered.

It is not always necessary to provide the auxiliary electrodes 2| and 22. In Figure 2, lead-in wires l9 and 20 serve as auxiliary electrodes .as well as lead-in wires. In this'case, the auxiliary Filament I one main electrode. y

In Figure 3, I show my} invention as applied to a two filament or double'filament' electricdischarge lamp in Which'the lamp is adapted to start with an auxiliary discharge shunting each filament. Electriodischarge lamp I3 is provided with filaments l4 and I5 and auxiliary electrodes 2| and 22, and 25 and 26. j 'I'o obtain, the desired action in igniting andj'operating' electric discharge lamp I3, I provide a. transformer l2 which cooperates with currentlimiting impedance, to automatically, andfwithout moving parts, carry forward the essential steps of this invention. Transformer l2. hasa main winding or exciting winding l6 and filament or starting'windings, ll and I8 which are'connected directly to filaments The combination of filament l4 and. auxiliary electrodes 2| and 22 form one main electrode in the type of low voltage electric dis- 1 H and II respectively. When so connected transformer I2 is in parallel circuit relation with lamp l3. windings l1 and I8 are so propor- 'tionedwith respect to the filaments l4 and'l! and auxiliary discharge gaps 28 and 24, that upon 1 being: connected topower supply l0, through choke 'l I, the filaments are heated to their rated value and auxiliary discharges are produced through discharge gaps23and 24., windings l1 and 18 are also proportioned with winding It so as to supply voltage across discharge tube II, that I is between the main electrodes sumcient to ignite the u eif the starting voltageapplied to the main electrodes, before ignition but during the time the filaments are being heated and the auxiliary dis-'- In actual practice I have found that charges are "occurring islmade at least twice the operating .voltag efof'larnptl 3, that this is suitable for taking care of fiuctuationsin commercial supply voltage. It' should be 1 pointed out that this startmgyoltage can be increased or decreased if it is' 'desired, :by; chan ng-the connection to the taps" oniwinding 15 of; 'trahSIOmier '12 as will be explained in connection "with: Figure i when ignition occurs' in lamp l3, an additional current flows through inductance "andireduce's-the voltage on transformer l2'andc onsfeulie itly upon the filaments II and I5; This reductioniin volt age is 'sumcient to extinguishthetauxiliaryyarcs through gaps 23 and, but maintains *areduced 4 anq ujq w m current flow through filaments i the filaments maintained" loss in the filamentsisjrduce During the starting condi auxiliary discharge are fact a's former l2.

ference caused by the operation of" the discharge,

lamp and is not used to tune any of the circuit elements. I therefore consider my lamp starting and operating device as an untuned circuit. 7

I have explained the operation ofmy invention as using the auxiliary arc-discharge for starting and because of its many advantages I prefer this method of operation. However, I should point outthat my invention as shown'in Figure 3'may be designed to satisfactorily startand operate 1 electric discharge lamps'flwithwtproducing the auxiliary arc discharge providing lossesare not considered important. j- -Ap'plying" my invention as shown, inFigure 3,

. '51 have found that this method ofqstarting does not cause the starting filaments to deteriorate ilrapidly. '-In comparativetests made with typical commercial starters similar to those previously:

mentioned, I have foundthat'the electric dishargejlamps do not tend to blacken even after prolonged starting tests when operated in accordase-limb my invention. Using a commercially -ifavailable' starting arrangement for a test, I

anYele'ctric discharge lamp at intervals 1 once perminutawith 54 seconds on and 6 secl oil, it was noted that blackening tended to occuriat'theendof 3vdays. Qn thissame duty 75 tro t iememes ena oa :transcycle using my invention to cause an auxiliary arc discharge as described above, blackening did not occur until approximately 6 weeks after the start of the test. In this test the lamps were operated continuously until they failed. Also, my invention seems to prolong the life of the lamp. This may be due to the use of the auxiliary arc and the low starting voltages combined with the continuously heated filament at a reduced temperature.

In another series of comparative tests made to ascertain the number of possible starts that might be obtained from a given lamp, my experiments show that in general, using my invention, ap-

proximately the full life of the lamp is obtained and therefore, the number of starts depends upon the duty cycle. With commercially, available starters impressing a high voltage across the lamp for starting, the life of the lamp seems to be definitely limited by the number of starts. Using commerciallyavailable starters, my tests indicate that-30,000 to 40,000 starts causes lamp failure even though the actual burning time of thelamp may be relatively short. As a comparison using my invention on slow flashing, I have obtained normal life of the lamp after having flashed the lamp 70,000 times. On, rapid flashing I have obtained good lamp life with over 2,000,000 flashes. In the rapid flashing tests, the lamp was flashed once per second, one-half second on. and onehalf second off.

Figure 4 shows my invention applied to an flelectric discharge lamp in which transformer l2 contains taps 3|, 32 and 33. By moving lead 30 from tap 32 to tap 3| a lower starting will be applied to lamp l3. However, by shifting lead 30 from tap 32 to tap 33 a higher starting voltage will be impressed upon lamp I3. I prefer to design filament windings I 1 and I8 so as to maintain a given auxiliary arc discharge during the starting period. By adjusting lead 30 to the proper tap on transformer l2 it is possible to arrive at an adjustment which will give minimum loss in the starting unit during normal operation of the lamp. Since the total loss during the operation of the lamp'will depend upon the losses in filaments I4 and I5 and the losses in transformer I2 and inductance II, it is necessary to design the starting unit for a given size discharge lamp where a miximum efliciency is to be obtained.

Figure 5 shows a' typical set of loss curves takenupon the various units of my invention as shown and described in connection with Figures 3 and 4. Figure 5 shows the losses of the series choke or inductance and the losses in the filaments and transformer plotted against the ratio of the starting winding l8 compared to the totalwinding used for impressinga starting volt- I age across lamp I3. It will be seen that the total loss in this particular instance was a minimum when the voltage impressed upon lamp H was slightly less than twice the voltage across winding I 6. It should be noted that the total loss shown by the curve in Figure 5 is represent- 7 ed by a V curve and hence has a very definite minimum loss. There may be other ways of arriving at this same design but the method described in connection withFigure 4 has been found satisfactory in a number of cases.

Referring to Figure 6 a starting unit made in accordance with my invention is shown in the form of a leakage reactance type of transformer. In this embodiment of my invention, series inductance II and transformer l2 are incorporated on the same core but are separated by a magnetic shunt 43. In carrying out my invention in this form I preferred to utilize auto-type transformer connections in order to reduce losses to a minimum. In using this construction the operation and starting cycle is substantially the same as described in connection with Figure 3.

In Figure '7, I show how my invention may be applied to operate an electric discharge lamp utilizing only one filament and one auxiliary discharge for starting purposes. One main electrode remaining cold during the starting process. The starting cycle of the circuit shown in Figure 7 is similar in all respects to the starting cycle described in connection with Figure 3 with the exception that only one electrode is utilized to produce ionization for starting purposes. It should be pointed out that in starting an electric discharge lamp with one electrode cold it is necessary to impress a higher voltage upon the discharge lamp to cause ignition. To do this I prefer to have lead 34 connected to tap 3| as shown in Figure 7 and thus obtain the increased potential necessary for causing ignition of lamp In Figure 8, I show another modification of my lamp starting invention. In this modification I replace transformer I2 by a saturable or nonlinear inductance 35. In the working of this embodiment of my invention I prefer to have filaments I4 and I in electric discharge lamp I3 capable of lighting to full brilliancy on current values substantially below the current value upon which lamp I3 normally operates. Also, I prefer to utilize auxiliary discharge gaps 23 and 24 to promote starting.

As before, I establish and maintain a starting condition which is automatically changed to an operating condition when lamp I3 ignites. Filaments I4 and I5 of lamp I3 are designed to op erate at rated brilliancy upon a fraction of the current normally taken by the lamp after ignition. While the filament and auxiliary electrode construction in the lamp may be of any suitable design, when operated by my invention as shown in Figures 8 and 9, I prefer to utilize filaments and auxiliary electrodes made to operate as shown, described and claimed in my copending application for U. S. Letters Patent Serial No. 266,971, filed April 10, 1939. Referring to Figure 8, saturable inductance 35 is connected in series with filaments I4 and I5 and is connected in parallel circuit relation with lamp I3. Substantially linear inductance II is connected between this combination and the source of alternating current. Under the starting condition, inductance 35 saturates and its impedance is lowered so that sufficient current flows through filaments I4 and I5 to cause them to operate at their rated brilliancy. Under this condition, I prefer to have auxiliary discharges take place through gaps 23 and 24. Since the starting condition takes only a fraction of the current taken by lamp I3 in normal operation, it is possible to impress sufficient voltage across lamp I3 to permit ignition as soon as lamp I3 is conditioned for starting.

When lamp I3 ignites, the main discharge occurs between the main electrodes. It is to be understood that a main electrode may comprise a filament and auxiliary discharge electrodes as described in connection with the detailed drawings in Figures 1 and 2. The main discharge will take place between any two main electrodes and charge lamps.

the discharge may localize upon any one part of a main electrode or any combination of parts in the main electrode. This can be more readily understood by referring again to detailed Figures 1 and 2. When lamp I3 ignites the voltage across lamp I3 is reduced from its starting voltage to the normal operating voltage of the lamp. The reduction in voltage across the lamp and also across saturable or non-linear inductance 35 reduces the flux density in the magnetic core of inducance 35 so that it is no longer saturated. Under this condition, the impedance of inductance 35 increases greatly thereby reducing the current flow through filaments I4 and I5, extinguishing auxiliary arcs through gaps 23 and 24 and reducing the loss due to the starting mechanism to a Under the normal operating condition, a small amount of current is still permitted to pass through filaments I4 and I5. As soon as lamp I3 ignites, the lamp is operated at the proper current values by current limiting impedance II.

While I show capacitor 29 in circuit relation with the current limiting impedance II and nonlinear impedance 35, it should be pointed out that this capacitor is used only for suppressing radio interference caused by discharge lamp I3 and is not used for tuning purposes in my invention. It is to be clearly understood that the various elements used in my invention form an untuned circuit.

Although it is necessary to have an electric discharge lamp with properly designed filaments to permit working of my invention as shown in Figure 8, a distinct advantage is gained thereby because inductance II and saturable inductance 35 may be made considerably smaller than the corresponding pieces used in my invention as shown in Figure 3.

Also, due to the tremendous change in the impedance of inductance 35, I am able to greatly reduce the losses of the starting unit.

The embodiment of my invention shown in Figure 9 may be classed as a universal circuit for starting and operating low voltage electric dis- 1 refer to it as a universal circuit because if current limiting impedance 44 is a substantially linear resistance and impedance element 45 is a suitable non-linear resistance a correctly designed electric discharge lamp may be operated from either alternating current or direct current. This is accomplished without the use of moving parts. Whenever the lamp starting and operating circuit shown in Figure 9 is to be operated from direct current or where it is desirable that the circuit operate as a universal starting and operating circuit, I prefer to use a non-inductive resistance for impedance 44 and a non-linear resistance for impedance 45. However, where lamp I3 is to be operated upon alternating current impedance 44 may be any suitable linear impedance and impedance 45 may be any suitable nonlinear impedance. Where only alternating current operation is desired the starting and operating circuit shown in Figure 8 is preferred.

Impedance 45 as used in my universal lamp starting and operating circuit may have characteristics similar to the material shown and described in U. S. Letters Patent 1,822,742, issued to K. D. McEachron, September 8, 1931, which material is similar to that known under the trade name of Thyrite. In some cases it may be desirable to utilize the non-linear properties of cuprous oxide rectifiers connected to act as a non-linear resistance and to pass alternating current in both directions.

In Figure 9, current shunting means represented by non-linear impedance 4! is arranged to have a lower resistance during the starting condition of lamp it than during the operating condition of lamp II. Current limiting means represented by linear impedance 44 is designed to permit during starting substantially full voltage from source II to be applied to the lamp. Similar to the action of the circuit described in connection with Figure 8, I prefer to have the filaments I4 and II in lamp l3 designed to operate at rated brilliancy upon a fraction of the current used by lamp in normal operation. With lamp l9, designed to have a main discharge current larger than the current through the filaments, I am able to proportion linear impedance 44 and non-linear impedance 45 so that substantially the full voltage of source III is applied across-lamp l3. Since the starting voltage is higher than the operating voltage of lamp l3, non-linear impedance 4! will have its impedance substantially reduced, which permits sufiicient current to fiow through filaments l4 and I5. 1- ring the starting condition sufiicient voltage must be impressed across lamp II to cause lamp ignition which is the same as causing the lamp to light.

During the starting condition I prefer to have the auxiliary arc discharge maintained to provide ready ignition at the voltage available across the main discharge electrodes of lamp I I. As soon as lamp ll ignites the lamp assumes a lower voltage, due to the increased current fiow through current limiting impedance 44, when the main discharge occurs.

As previously explained, this decrease in voltage across lamp I 3 causes non-linear impedance 45, which acts as an untuned current shunting means across the lamp, to increase its impedance and thereby reduce filament heating. Under this condition the auxiliary arc discharges which may be maintained during the starting condition are extinguished during the normal operation of the lamp.

"In the working of my invention as shown and described in connection with Figures 8 and 9, I prefer to have the main electrodes of lamp l3 constructed so that the main discharge occurs on some part of the main electrode which prevents damage to the fragile filaments. Since the main discharge current is greater than the filament current in this embodiment of my invention it is desirable to have the filaments relieved from carrying the greater part of the main discharge. While any suitable construction of the main discharge electrodes may be used, I prefer to use an electric discharge lamp similar to those shown and described in my copending U. S.-Patent application Serial No. 266,971, filed April 10, 1939.

Figure 10 shows a modification of my invention which uses in combination with substantially linear inductance II, a saturable autotransforrner designated as 36. This particular modification of my invention differs from my previous disclosures in that the filament is lightv ed in series with inductance II and winding 31 of transformer '36. As described in connection with Figure 8, I prefer to have filament l designed so that it will operate: at proper brillianey upon a fractionof the current used by lamp ii in normal operation. Under the starting condition, transformer 36 is designed to work at saturation so that the impedance of winding 31 will be low enough to permit rated current to fiow through filament l5. Inductance II is approximately linear and is used to limit the current when lamp ll ignites. Under the starting condition, current flows through winding 31 and filament and causes transformer It to impress an increased voltage across lamp It. At the same time, ionization caused by the heating of filament I I and discharge through auxiliary gap 24 conditions lamp II for ignition. When ignition occurs, the voltage across lamp I3 is reduced. This reduction in voltage across lamp I I at ignition is sufilcient to permit transformer 36 to establish an unsaturated condition. This consequently increases the impedance of winding 31 and permitsa reduced current flow through filament l5 and extinguishes auxiliary arc discharge through gap 24.

In Figure 11, I show the preferred arrangement of my invention when usedlin flashing an electric discharge lamp. Fundamentally, my invention shown in Figure 11 is the same as my invention shown in Figure 3. However, in Figure ll circuit interrupting device 39 has been added in series'with my lamp starting invention. I have found in the operation of my invention that if capacitor 49 in series with resistance 4l is used'to shunt interrupter 39, it is possible by' correctly proportioning condenser and resistance 4| to maintain a heated condition in filaments l4 and IS without the accompanying auxiliary discharge in gaps 23 and 24 during.

the off period of interrupter 39. Tests indicate that additional lamp life may be expected if filaments I 4 and ii are permitted to operate at a predetermined but lowered heat level during the off period of interrupter 39. This is accomplished by current from source Ill flowing through capacitor 44 and resistance 4|, during the oif period of interrupter 39. It therefore seems desirable to make this modification where long lamp life isdesired in flasher operation of electric discharge lamps.

In order to simplify and clarify the description of my invention, I have omitted mentioning capacitor 29 with reference to each figure. Capacitor 29 is used to shunt the tube or lamp IS in order to minimize radio interference set up by the main gaseous discharge during normal operation. The value of this capacitor is not critical as it is not used for tuning purposes. A satisfactory capacitor size has been found to be between .005 and .05 mfd. for use with 15 and 20 watt fluorescent low voltage discharge lamps.

In my description I have tried to point out clearly that there are two 'iiifierent conditions applied to the tube or lamp-a starting condition and an operating condition-and that the starting condition permits lamp ignition at low voltages and that the ignition of the lamp automatically causes the starting condition to be changed to the operating condition.

In the following claims I refer to linear in-- ductance or substantially linear inductance and by this I mean an inductance having a magnetic core, which core is operated below saturation.

Also in the following claims I refer to electric discharge lamps having one or more filaments, or

having at least one filament sealed therein or the disposition of the various elements located within the lamp so long as the operation is similar to that described in this specification.

In Figure 9, source I is shown as an alternator, but since this embodiment of my invention may be made to operate upon either alternating current or direct current it is to be understood that in this particular case source It may be any suitable source of electrical energy.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way 0! example and that-numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

I claim as my invention:

1. A circuit for starting and operating a low voltage electricdischarge lamp from a source of alternating current in which the operating voltage across said lamp is less than the voltage of the supply source, comprising in combination, a linear inductance, a non-linear inductance, an electric discharge lamp having two filaments sealed therein, said non-linear inductance being connected in series with the two filaments and in parallel with said discharge lamp to form a continuous circuit, and means ior connecting said linear inductance in series with said continuous circuit and with said source of alternating current, said non-linear inductance being saturated during the starting condition of the lamp and non-saturated during the operating condition.

tion which includes heating said filaments and saturating the non-linear inductance to cause ignition of the electric discharge lamp, the ignition of said lamp causing the impedance of said a non-linear inductance to increase and change the lamp starting condition to a lamp operating condition.

3. An alternating current device for connectin an electric discharge lamp having filaments sealed therein with alsource of alternating current comprising a linear inductance, a saturable inductance and a capacitor, said satm'able inductance being connected in parallel with the lamp and in series with the filaments, said linear inductance being connected in series with a source of alternating current and with said lamp filaments, said saturable inductance being adapted to be saturated before ignition oi the lamp and unsaturated aiter ignition occurs in the lamp, and means for connecting said capacitor in parallel with said lamp.

CLOSMAN P. STOCKER. 

